Sheet processing apparatus and image forming system having the same

ABSTRACT

To provide a sheet processing apparatus capable of preventing interference between a next sheet to be conveyed and a discharge claw member after a sheet bundle is discharged by the discharge claw member and reducing the occurrence of a conveyance jam due to curling or buckling of the front end of the next sheet. A sheet processing apparatus includes: a first support guide integrally provided at the upstream end portion in a sheet conveying direction of a discharge unit, which discharges a sheet placed on a processing tray by pushing the rear end portion of the sheet in the sheet conveying direction, and configured to support the downstream front end portion in the conveying direction of a sheet to be conveyed onto the processing tray; and an aligning unit that aligns the sheet on the processing tray in a sheet width direction perpendicular to the conveying direction.

TECHNICAL FIELD

The present invention relates to a sheet processing apparatus that processes a sheet fed from an image forming apparatus and the like and an image forming system having such a sheet processing apparatus.

BACKGROUND ART

There is widely known a post-processing apparatus that stacks sheets discharged from an image forming apparatus on a processing tray, binds the sheets using a binding device, and stores the resultant sheet bundle on a stack tray arranged at a downstream location. Such an apparatus may employ a stand-alone structure, in which sheets are fed along a sheet carry-in path connected to a sheet discharge port of the image forming apparatus, collated and stacked on a processing tray disposed at the discharge port of the sheet carry-in path, subjected to binding processing by a binding processing unit disposed on the processing tray, and finally stored on a stack tray disposed at a downstream location. Further, the apparatus may employ an inner finisher structure that incorporates, at a sheet discharge area of the image forming apparatus, a unit equipped with a processing tray having a binding unit and a stack tray.

Such an apparatus requires a bundle conveying mechanism for conveying a sheet bundle that has been subjected to binding processing or that has once been stacked on a processing tray to a stack tray provided on the downstream side. For example, Patent Document 1 and Patent Document 2 disclose a post-processing apparatus disposed downstream from an image forming apparatus configured to: receive image-formed sheets from the image forming apparatus; collate and stack the sheets; perform binding processing for the sheets; and store the resultant sheet bundle on a stack tray. In the post-processing apparatus in these documents, the processing tray is equipped with a sheet bundle carry-out mechanism for carrying out a sheet bundle from a binding position to the stack tray provided on the downstream side. The sheet bundle carry-out mechanism has a claw member (projecting member) which is integrally provided on a belt supported by a drive pulley so as to be engaged with the rear end edge of a sheet bundle. This claw member is configured to be movable along a tray surface from the binding end portion of the processing tray to a carry-out end portion.

Patent Document

Patent Document 1: Japanese Patent Application Laid-Open No. 2015-020822

Patent Document 2: Japanese Patent Application Laid-Open No. 2007-076893

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

Examples of the mechanism for carrying out a sheet bundle from a processing tray on which a sheet bundle is collated, stacked, and bound, to a stack tray arranged at a downstream location include a mechanism that pushes out the sheet bundle using a belt conveyer and a mechanism that carries out a sheet bundle using a roller pair. In the belt conveyer mechanism, a pair of pulleys are provided at the bottom portion of the processing tray, over which a belt (carrier member) is stretched, and a claw member (projecting member) for locking the rear end edge of a sheet bundle is integrally attached to the belt. This allows the claw member to be moved along the tray upper surface from the tray rear end to front end, providing good discharge performance. However, such a sheet bundle carry-out mechanism has the following problem. That is, the claw member reciprocates with a long stroke, i.e., performs a forward movement from the tray rear end to front end (toward an apparatus discharge port) and a return movement from the tray front end to rear end, and at the time when the claw member returns from the tray front end, it may collide with the next sheet to be conveyed to the processing tray to cause a conveyance jam.

An object of the present invention is to prevent interference between the next sheet to be conveyed and a discharge claw member after a sheet bundle is discharged by the discharge claw member and to reduce the occurrence of a conveyance jam due to curling or buckling of the front end of the next sheet.

Means for Solving the Problem

To solve the above problem, a sheet processing apparatus according to the present invention includes: a conveying unit that conveys a sheet in a predetermined conveying direction; a processing tray on which the sheet conveyed by the conveying unit is placed; a discharge unit that discharges the sheet placed on the processing tray by pushing the rear end portion of the sheet in the sheet conveying direction; a stack tray on which the sheet discharged by the discharge unit is stacked; an aligning unit that aligns the sheet on the processing tray in a sheet width direction perpendicular to the conveying direction; a first support guide integrally provided at the upstream end portion of the discharge unit in the conveying direction and configured to support the downstream front end portion in the conveying direction of a sheet to be conveyed onto the processing tray; and a controller that controls the discharge unit and the aligning unit. The controller controls, after a sheet is discharged from the processing tray to stack tray, the first support guide to support the downstream front end portion in the conveying direction of a next sheet to convey the sheet onto the processing tray.

Advantageous Effect of the Invention

There can be provided a sheet processing apparatus capable of reducing the occurrence of a conveyance jam during sheet conveyance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory view illustrating the entire configuration of an image forming system according to the present invention;

FIG. 2 is an explanatory perspective view illustrating the entire configuration of a post-processing apparatus in the image forming system of FIG. 1;

FIG. 3 is a cross-sectional side view (at an apparatus front side) of the apparatus of FIG. 2;

FIGS. 4A and 4B are explanatory views of a sheet carry-in mechanism of the apparatus of FIG. 2, in which FIG. 4A illustrates a state where a paddle rotor is at a waiting position and FIG. 4B illustrates a state where the paddle rotor is at an engaging position;

FIG. 5 is an explanatory view illustrating the arrangement of individual areas and alignment positions in the apparatus of FIG. 2;

FIG. 6 is an explanatory view of the configuration of a side aligning unit in the apparatus of FIG. 2;

FIG. 7 is an explanatory view of a moving mechanism of a stapling unit;

FIG. 8 is an explanatory view illustrating the binding position of the stapling unit;

FIG. 9 is an explanatory view of multi-binding and left corner binding performed by the stapling unit

FIGS. 10A to 10C illustrate a state of the stapling unit at the binding position, in which FIG. 10A illustrates a state at a right corner binding position, FIG. 10B illustrates a staple loading position, and FIG. 10C illustrates a state at a manual binding position;

FIG. 11 is an explanatory view of a sheet bundle carry-out mechanism according to a first embodiment, which illustrates a waiting state;

FIG. 12 is an explanatory view of the sheet bundle carry-out mechanism according to the first embodiment, which illustrates a relay conveyance state;

FIG. 13 is an explanatory view of the sheet bundle carry-out mechanism according to the first embodiment, which illustrates the structure of a second conveying member;

FIG. 14 is an explanatory view of the sheet bundle carry-out mechanism according to the first embodiment, which illustrates a state where sheets are discharged onto a stack tray;

FIG. 15 is an explanatory view of the sheet bundle carry-out mechanism according to the first embodiment, which illustrates a state where a next sheet is conveyed to a processing tray;

FIG. 16 is an overall view illustrating a sheet bundle carry-out mechanism according to a second embodiment;

FIG. 17 is an explanatory view of the sheet bundle carry-out mechanism according to the second embodiment, which illustrates a waiting state;

FIG. 18 is an explanatory view of the sheet bundle carry-out mechanism according to the second embodiment, which illustrates a relay conveyance state;

FIG. 19 is an explanatory view of the sheet bundle carry-out mechanism according to the second embodiment, which illustrates a sheet conveyance state by the second conveying member;

FIG. 20 is an explanatory view of the sheet bundle carry-out mechanism according to the second embodiment, which illustrates a state immediately before the second conveying member reaches a discharge position and a state where the second conveying member starts returning from the discharge position to a waiting position;

FIG. 21 is an explanatory view of the sheet bundle carry-out mechanism according to the second embodiment, which illustrates a state where the second conveying member is located at the discharge position;

FIG. 22 is an explanatory view of a sheet bundle carry-out mechanism according to a third embodiment, which illustrates a state where the second conveying member is located at the discharge position;

FIGS. 23A to 23C are explanatory views of the drive configuration of the sheet bundle carry-out mechanism, in which FIG. 23A is a main part enlarged view, FIG. 23B illustrates a motor activation state; and FIG. 23C illustrates a state after rotation by a predetermined angle;

FIGS. 24A to 24G each illustrate a sheet bundle binding processing method;

FIG. 25A is an explanatory view illustrating the configuration of the stapling unit, and FIG. 25B is an explanatory view illustrating the configuration of a press binding unit;

FIG. 26 is an explanatory view illustrating the configuration of a stack tray in the apparatus of FIG. 2;

FIG. 27 is an operation flowchart for changing the operation depending on the size of a sheet to be carried in onto the processing tray;

FIG. 28 is an operation flowchart for changing the operation depending on the basis weight of a sheet to be carried in onto the processing tray;

FIG. 29 is an operation flowchart for changing the operation depending on the presence or absence of a shift operation for a succeeding job with respect to a preceding job that has been subjected to shift operation;

FIG. 30 is an explanatory view illustrating a state where the front end of a next sheet is supported above the aligning plate; and

FIG. 31A is a schematic view illustrating, as viewed from above, a state where the front end of a succeeding sheet S2 is supported by a second conveying member 60B after a preceding sheet bundle 51 is discharged, and FIG. 31B is a schematic view illustrating, as viewed from above, a state where the front end of the succeeding sheet S2 is supported by an aligning member 45 (46F) after the preceding sheet bundle 51 is discharged.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail based on illustrated preferred embodiments. The present invention relates to a sheet bundle binding processing mechanism that performs binding processing for a collated and stacked sheet bundle with images formed thereon in an image forming system to be described later. The image forming system illustrated in FIG. 1 includes an image forming unit A, an image reading unit C, and a post-processing unit B. A document image is read by the image reading unit C. Based on the image data, the image forming unit A forms an image on a sheet. Then, the post-processing unit B (sheet bundle binding processing apparatus) performs binding processing with the image-formed sheets being collated and stacked and stores the sheets on a stack tray 25 arranged at a downstream location.

The post-processing unit B to be described later is incorporated as a unit in a sheet discharge space (stack tray space) 15 formed in the housing of the image forming unit A. The post-processing unit B has an inner finisher structure having a post-processing mechanism that performs, on a processing tray, binding processing after collating and stacking the image-formed sheets conveyed to a sheet discharge port 16 and then stores the sheets on the stack tray provided downstream from the processing tray. Not limited to the above, the present invention may have a stand-alone structure in which the image forming unit A, the image reading unit C, and the post-processing unit B are independently arranged, and the respective units are connected by network cables to be systematized.

[Sheet Bundle Binding Processing Apparatus (Post-Processing Unit)]

As illustrated in FIGS. 2 and 3 being a perspective view and a cross-sectional view of the post-processing unit B, the post-processing unit B includes an apparatus housing 20, a sheet carry-in path 22 disposed in the apparatus housing 20, a processing tray 24 disposed downstream from a sheet discharge port 23 of the sheet carry-in path 22, and a stack tray 25 disposed downstream from the processing tray 24.

The processing tray 24 is provided with a sheet carry-in unit 35 for carrying in a sheet, and a sheet end regulating unit 40 and an aligning unit 45 which are used for stacking carried-in sheets in a bundle form. In addition, the processing tray 24 is provided with a stapling unit 26 (first binding unit) for performing staple-binding for a sheet bundle and a non-stable binding unit 27 (second binding unit) for performing non-staple binding for a sheet bundle. Each component will be described below in detail.

[Apparatus Housing]

The apparatus housing 20 includes an apparatus frame 20 a and an external casing 20 b. The apparatus frame 20 a has a frame structure to support mechanisms (a path mechanism, a tray mechanism, a conveying mechanism, etc.) to be described later. In the drawings, a binding mechanism, the conveying mechanism, a tray mechanism, and a driving mechanism are arranged at a left-right pair of side frames (not illustrated) which are mutually opposed to form a monocoque structure so as to be integrated with the external casing 20 b. The external casing 20 b has the monocoque structure obtained by integrating, through mold processing using resin or the like, left-right side frames 20 c, 20 d and a stay frame (bottom frame 20 e to be described later) connecting the side frames 20 c and 20 d. A part (at the apparatus front side) of the external casing 20 b is exposed to be operable from the outside.

That is, the frames are stored in the sheet discharge space 15 of the image forming unit A to be described later with an outer circumference thereof covered with the external casing 20 b. In the above state, the front side of the external casing 20 b is exposed to be operable from the outside. A later-described cartridge mount opening 28 for staples, a manual feed setting part 29, and a manual operation button 30 (in the drawing, a switch having a built-in lamp) are arranged at the front side of the external casing 20 b. The external casing 20 b has a length Lx in the sheet discharge direction and a length Ly in a direction perpendicular to the sheet discharge direction which are set based on the maximum sheet size so as to be smaller than the sheet discharge space 15 of the later-described image forming unit A.

[Sheet Carry-In Path (Sheet Discharge Path)]

As illustrated in FIG. 3, the sheet carry-in path 22 (hereinafter, referred to as “sheet discharge path”) having a carry-in port 21 and the sheet discharge port 23 is disposed in the above-mentioned apparatus housing 20. The illustrated sheet discharge path 22 is configured to receive a sheet in the horizontal direction and discharge the sheet from the sheet discharge port 23 after conveying approximately in the horizontal direction. The sheet discharge path 22 includes an appropriate paper guide (plate) 22 a and incorporates a feeder mechanism for sheet conveyance. The feeder mechanism is constituted by pairs of conveying rollers arranged so as to be spaced apart by predetermined intervals in accordance with the path length. In FIG. 3, a carry-in roller pair 31 is disposed in the vicinity of the carry-in port 21, and a discharge roller pair 32 is disposed in the vicinity of the sheet discharge port 23. A sheet sensor Se1 to detect a sheet front end and/or a sheet rear end is disposed in the sheet discharge path 22.

The sheet discharge path 22 includes a linear path arranged approximately in the horizontal direction so as to traverse the apparatus housing 20 so as to prevent stress caused by a curved path from being applied to a sheet and is formed as having linearity which is allowed by apparatus layout. The carry-in roller pair 31 and discharge roller pair 32 are connected to the same driving motor M1 (hereinafter, referred to as “conveying motor”) and convey a sheet at the same circumferential speed.

[Processing Tray]

Referring to FIG. 3, the processing tray 24 is disposed downstream from the sheet discharge port 23 of the sheet discharge path 22 so as to form a step d therefrom. For upward stacking of sheets fed from the sheet discharge port 23 in a bundle form, the processing tray 24 includes a sheet placing surface 24 a supporting at least a part of the sheet. FIG. 3 illustrates a structure (bridge-support structure) in which the sheet front end side is supported by the later-described stack tray 25 and the sheet rear end side is supported by the processing tray 24. Thus, the processing tray 24 is downsized.

On the above processing tray 24, the sheets fed from the sheet discharge port 23 are stacked in a bundle shape, aligned to a predetermined posture, and subjected to binding processing. The resultant sheet bundle is carried out to the stack tray 25 arranged at a downstream location from the processing tray 24. To this end, the processing tray 24 has a sheet carry-in mechanism 35, a sheet aligning mechanism 45, binding processing mechanisms 26, 27, and a sheet bundle carry-out mechanism 60.

[Sheet Carry-In Mechanism (Sheet Carry-In Unit)]

Since the processing tray 24 is disposed so as to form the step d from the sheet discharge port 23, it is required to provide the sheet carry-in unit 35 for smoothly conveying a sheet onto the processing tray 24 with a proper posture. The illustrated sheet carry-in unit 35 (friction rotor) is constituted by a paddle rotor 36, which is configured to move up and down. When a sheet rear end is discharged from the sheet discharge port 23 onto the processing tray 24, the paddle rotor 36 conveys the sheet in a direction (rightward in FIG. 3) opposite to the sheet discharge direction to cause the sheet to abut against a later-described sheet end regulating unit 40 to be aligned (positioned).

An elevating arm 37 axially and swingably supported by a support shaft 37 x to the apparatus frame 20 a is disposed at the sheet discharge port 23. The paddle rotor 36 is axially rotatably supported to the top end part of the elevating arm 37. A pulley (not illustrated) is provided at the support shaft 37 x, and the abovementioned conveying motor M1 is connected to the pulley.

In addition, the elevating arm 37 is connected with an elevating motor (hereinafter, referred to as “paddle elevating motor”) M3 through a spring clutch (torque limiter) and is configured to be elevated and lowered by rotation of the puddle elevating motor M3 between a waiting position Wp at the upper side and an operating position (sheet engaging position) Ap at the lower side. That is, the spring clutch elevates the elevating arm 37 from the operating position Ap to the waiting position Wp by rotation of the paddle elevating motor M3 in one direction and keeps the elevating arm 37 waiting at the waiting position Wp after abutting against a stopper (not illustrated). On the contrary, the spring clutch is released by rotation of the paddle elevating motor M3 in the opposite direction to cause the elevating arm 37 to be lowered under its own weight from the waiting position Wp to the operating position Ap on the lower side to be engaged with the upmost sheet on the processing tray.

In the illustrated apparatus, a pair of the paddle rotors 36 are arranged in a symmetric manner with respect to a sheet center Sx (center reference Sx) so as to be apart from each other at a predetermined distance, as illustrated in FIG. 5. Alternatively, three paddle rotors in total may be arranged, i.e., at the sheet center and both sides thereof, or one paddle rotor may be arranged at the sheet center.

The paddle rotor 36 is constituted by a flexible rotor formed of a rubber-made plate-shaped member, plastic-made blade member, or the like. Instead of the paddle rotor 36, the sheet carry-in unit 35 may be constituted by a friction rotating member such as a roller body or a belt body. In the above description, the illustrated apparatus includes the mechanism in which the paddle rotor 36 is lowered from the waiting position Wp at the upper side to the operating position Ap at the lower side after the sheet rear end is discharged from the sheet discharge port 23; instead of the above, it is possible to employ an elevating mechanism to be described below.

With an elevating mechanism different from the illustrated mechanism, for example, at the timing when the sheet front end is discharged from the sheet discharge port 23, a friction rotor is lowered from a waiting position to an operating position and rotated concurrently in the sheet discharge direction. Then, at the timing when the sheet rear end is discharged from the sheet discharge port 23, the friction rotor is reversely rotated in a direction opposite to the sheet discharge direction. With this operation, a sheet discharged from the sheet discharge port 23 can be conveyed to a predetermined position on the processing tray 24 at high speed without being skewed.

[Raking Rotor (Raking Conveying Unit)]

When a sheet is conveyed to a predetermined position on the processing tray 24 by the sheet carry-in mechanism 35 (paddle rotor) disposed at the sheet discharge port 23, a raking conveying unit 33 is required to guide the front end of the sheet (in particular, the front end of a curled or skewed sheet) to the sheet end regulating unit 40 provided at a downstream location.

In the illustrated example, a raking rotor (raking conveying unit) 33 that conveys the uppermost sheet of sheets stacked upstream of the sheet end regulating unit 40 to be described later toward the sheet end regulating member side is disposed below the sheet discharge roller pair 32. The raking rotor 33 includes a ring-shaped belt member 34 (hereinafter, referred to as “raking belt”) which is disposed above the top end part of the processing tray 24. The raking belt 34 is engaged with the uppermost sheet of the sheets stacked on the sheet placing surface and rotates in such a direction as to convey the sheet to the regulating member side.

The raking belt 34 is constituted by a high-friction belt member (roulette belt or the like) formed of a flexible material such as rubber and is supported so as to be nipped between a rotary shaft 34 x connected to a drive motor (the one illustrated is the conveying motor M1) and an idle shaft 34 y. The raking belt 34 is imparted with a torque in the counterclockwise direction depicted in FIG. 3 from the rotary shaft 34 x. The raking belt 34 makes the front end of a sheet carried in along the uppermost sheet of the sheets stacked on the processing tray 24 abut against the sheet end regulating unit 40 downstream while pressing the carried-in sheet.

The raking belt 34 is configured to be elevated and lowered above the uppermost sheet of the sheets stacked on the processing tray 24 by a belt shift motor M5 (hereinafter, referred to as “roulette elevating motor”) (description of the elevating mechanism is omitted). The raking belt 34 is lowered at the timing when the sheet front end enters between the belt surface and the uppermost sheet to be engaged with the carried-in sheet. Further, when conveying a sheet bundle from the processing tray 24 to the stack tray 25 provided downstream therefrom using a sheet bundle carry-out unit 60 to be described later, the roulette elevating motor M5 is controlled such that the raking belt 34 is separated from the uppermost sheet and waits thereabove.

[Sheet Aligning Mechanism]

The processing tray 24 is provided with a sheet aligning mechanism 45 that positions a carried-in sheet to a predetermined position (processing position). The illustrated sheet aligning mechanism 45 includes the “sheet end regulating unit 40” for regulating the position of the end surface (front end surface or rear end surface) in the sheet discharge direction of a sheet fed from the sheet discharge port 23 and the “side aligning unit 45” for aligning (width-aligning) a sheet in a direction (sheet side direction) perpendicular to the sheet discharge direction. Hereinafter, the sheet end regulating unit 40 and the side aligning unit 45 will be described in this order.

[Sheet End Regulating Unit]

The illustrated sheet end regulating unit 40 is constituted by a rear end regulating member 41 for abutment-regulating the rear end of a sheet in the sheet discharge direction. The rear end regulating member 41 has a regulating surface 41 a for abutment-regulating the rear end edge of a sheet in the sheet discharge direction carried in along the sheet placing surface 24 a of the processing tray 24. The rear end edge of the sheet in the sheet discharge direction conveyed by the above raking conveying unit 33 abuts against the regulating surface 41 a and is stopped.

When multi-binding is performed with a stapling unit 26 to be described later, the stapling unit 26 is moved along the sheet rear end (in a direction perpendicular to the sheet discharge direction). To prevent obstruction against the movement of the stapling unit 26, the rear end regulating member 41 is configured to adopt any one of the following structures of:

(1) adopting a mechanism in which the rear end regulating member proceeds to and retracts from a movement path (motion trajectory) of the binding unit;

(2) adopting a mechanism in which the rear end regulating member is moved integrally with the binding unit; and

(3) forming the rear end regulating member, for example, as a channel-shaped folded piece disposed inside a binding space which is formed by a head and an anvil of the binding unit.

In the illustrated example, the rear end regulating member 41 is constituted by a plate-like bent member having a U-shape (channel shape) in cross section and disposed in the binding space of the stapling unit 26. With the minimum size sheet as a reference, a first member 41A is disposed at the sheet center, and second and third members 41B and 41C are disposed on both sides of the first member 41A so as to be spaced apart therefrom (see FIG. 5). This allows the stapling unit 26 to be moved in the sheet width direction.

As illustrated in FIGS. 5 and 7, a plurality of the rear end regulating members 41 formed of channel-shaped folded pieces are fixed to the processing tray 24 with leading end parts thereof fixed to a back surface wall of the processing tray 24 with screws. The regulating surface 41 a is formed at each of the rear end regulating members 41 and an inclined surface 41 b for guiding a sheet end to the regulating surface 41 a is continuously formed at the leading end part of the folding thereof.

[Side Aligning Unit]

The processing tray 24 is provided with the aligning unit 45 (hereinafter, referred to as “side aligning member”) for positioning a sheet abutting against the above rear end regulating member 41 in a direction (hereinafter, referred to as “sheet width direction”) perpendicular to the sheet discharge direction.

The side aligning member 45 is configured differently based on whether sheets having different sizes are aligned on the processing tray 24 in center reference or side reference. In the apparatus illustrated in FIG. 5, sheets of different sizes are discharged from the discharge port 23 in the center reference, and the sheets are aligned on the processing tray 24 in the center reference. Then, binding processing is performed by the stapling unit 26 for a sheet bundle which is aligned into a bundle shape in center reference, in accordance with the binding processing, at binding positions Ma1 and Mat in an aligned posture for multi-binding and at binding positions Cp1 and Cp1 with the sheet bundle offset by a predetermined amount in the width direction for lateral corner binding.

To perform the above aligning operation, the aligning unit 45 is provided with a left-right pair of side aligning members 46 (46F, 46R) each protruding upward from the sheet placing surface 24 a of the processing tray 24 and each having a regulating surface 46 x engaged with the side edge of a sheet. The side aligning members 46F and 46R are disposed opposite to each other and configured to reciprocate on the processing tray 24 in a predetermined stroke. The stroke amount is set based on the difference in size between a maximum size sheet and a minimum size sheet and the amount of offset movement (offset conveyance) of the aligned sheet bundle to one side in the sheet width direction. That is, the stroke amount of each of the side aligning members 46F and 46R is set based on the movement amount for aligning sheets of different sizes and the movement amount for offsetting an aligned sheet bundle.

Thus, as illustrated in FIG. 6, the side aligning member 46 includes a right side aligning member 46F (on the apparatus front side) and a left side aligning member 46R (on the apparatus rear side). The side aligning members 46F and 46R are supported on the tray member such that the regulating surfaces 46 x thereof engaged with the sheet side ends are moved in a mutually approaching or separating direction. Slit grooves 24 x penetrating the processing tray 24 are formed in the processing tray 24. The side aligning member 46 having the regulating surface 39 x engaged with the side edge of a sheet is slidably fitted to the slit so as to protrude from the upper surface of the processing tray 24.

The side aligning members 46F and 46R are each integrally formed with a rack 47 and are slidably supported by a plurality of guide rollers 49 (or rail members) on the back surface side of the processing tray 24. Aligning motors M6 and M7 are connected to the left and right racks 47 respectively through a pinion 48. The left and right aligning motors M6 and M7 are each constituted by a stepping motor. Positions of the left and right aligning members 46F and 46R are detected by position sensors (not illustrated). Based on the detected values, the side aligning members 46F and 46R can be moved respectively in either left or right direction by specified movement amounts.

In place of the illustrated rack-and-pinion mechanism, a configuration may be adopted, in which the side aligning members 46F and 46R are each fixed to a timing belt, and the timing belt is connected, through a pulley, to a motor for reciprocating the belt laterally.

According to the above configuration, a controller 75 causes the left and right side aligning members 46 to wait at predetermined waiting positions (distanced by a sheet width+a therebetween) based on sheet size information provided from the image forming unit A or the like. In this state, a sheet is carried in onto the processing tray 24, and at the timing when the end of the sheet abuts against the rear end regulating member 41, an aligning operation is started. In the aligning operation, the left and right aligning motors M6 and M7 are rotated in opposite directions (approaching directions) by the same amount. Accordingly, sheets carried in onto the processing tray 24 are positioned and stacked in a bundle form in reference to the sheet center. According to the repetition of the sheet carry-in operation and aligning operation, sheets are collated and stacked on the processing tray 24 in a bundle form. At this time, sheets of different sizes are positioned in center reference.

The sheets thus stacked on the processing tray 24 in center reference can be subjected to binding processing at a plurality of positions separated from each other by a predetermined interval (i.e., multi-binding processing) in the above posture at the rear end (or front end) of the sheets. In a case of performing the binding processing on a sheet corner, one of the left and right side aligning members 46F and 46R is moved to and stopped at a position where a sheet side end matches a specified binding position. Then, the side aligning member on the opposite side is moved in the approaching direction. A movement amount in the approaching direction is calculated in accordance with the sheet size. Accordingly, a sheet carried in onto the processing tray 24 is aligned such that a right side end matches a binding position in a case of right corner binding and a left side end matches a binding position in a case of left corner binding.

When a sheet bundle thus aligned to a predetermined position on the processing tray 24 is offset-moved for eco-binding processing to be described later, one of the following drive controls is performed:

(1) drive control that the aligning member at the rear side in the movement direction is moved in a direction perpendicular to the sheet conveying direction by a preset amount in a state where the aligning member at the front side in the movement direction is retracted to a position separated from an offset assumed position; and

(2) drive control that the left-right aligning members are moved in a direction perpendicular to the sheet conveying direction by the same amount.

The left and right side aligning members 46F and 46R and the aligning motors M6 and M7 are each provided with a position sensor (not illustrated) such as a position sensor and an encode sensor for detecting the position of the side aligning member 46. Owing to that the aligning motors M6 and M7 are constituted by stepping motors, home positions of the side aligning members 46F and 46R are detected by position sensors (not illustrated), and the motors are PWM-controlled, so that the left and right side aligning members 46F and 46R can be controlled with a relatively simple control configuration.

[Sheet Bundle Carry-Out Mechanism]

The following describes a first embodiment of a sheet bundle carry-out mechanism (sheet bundle carry-out unit 60) with reference to FIGS. 11 to 13. The processing tray 24 is provided with a sheet bundle carry-out mechanism that carries out a sheet bundle bound by the first binding unit 26 or second binding unit 27 to the stack tray 25 provided downstream from the processing tray 24. On the processing tray 24 described based on FIG. 5, the first member 41A is arranged at the sheet center Sx, and the second and third members 41B and 41C are arranged laterally as being distanced therefrom. A sheet bundle stopped by the regulating member 41 is to be carried out to the stack tray 25 located downstream after being subjected to binding processing by the first binding unit 26 (27).

To achieve the above operation, the sheet bundle carry-out unit 60 is disposed along the sheet placing surface 24 a of the processing tray 24. The illustrated sheet bundle carry-out unit 60 includes a first conveying member 60A and a second conveying member 60B. Conveyance in a first section L1 on the processing tray 24 is performed by the first conveying member 60A and conveyance in a second section L2 is performed by the second conveying member 60B, whereby relay conveyance is performed. Since a sheet bundle is conveyed serially by the first and second conveying members 60A and 60B, the mechanisms of the first and second conveying members 60A and 60B can be made different. It is required that the member that conveys a sheet bundle from a starting point being approximately the same as the sheet rear end regulating unit 40 is formed of a less swaying member (elongated support member) and a member that causes the sheet bundle to drop at the end point of conveyance is downsized (for travelling on a loop trajectory).

The first conveying member 60A is constituted by a first carry-out member 61 formed of a folded piece having a channel shape in cross section. The first carry-out member 61 includes a stop surface 61 a that stops a rear end surface of a sheet bundle and a sheet surface pressing member 62 (an elastic film member; Mylar piece) that presses an upper surface of the sheet bundle stopped by the stop surface 61 a. As illustrated, the first conveying member 60A is formed of a folded piece having a channel shape in cross section. Accordingly, when being fixed to a carrier member 65 a (belt) to be described later, the first conveying member 60A moves (feeds) the rear end of the sheet bundle in the conveying direction by travelling integrally with the belt with less swaying. The first conveying member 60A reciprocates with a stroke Str1 on an approximately linear trajectory without travelling on a loop trajectory curved as will be described later.

The second conveying member 60B is constituted by a second carry-out member 63 having a claw shape. The second carry-out member 63 includes a stop surface 63 a that stops the rear end surface of a sheet bundle and a sheet surface pressing member 64 that presses the upper surface of the sheet bundle. The sheet surface pressing member 64 is axially swingably supported to the second carry-out member 63 and has a sheet surface pressing surface 64 a. The sheet surface pressing surface 64 a is biased by a biasing spring 64 b so as to press the upper surface of the sheet bundle.

The sheet surface pressing surface 64 a is constituted by an inclined surface inclined with respect to the traveling direction as illustrated. Accordingly, when the second conveying member 60B is moved in the direction of the arrow in FIG. 12, the sheet surface pressing surface 64 a is engaged with the sheet rear end at a nipping angle γ. At this time, the sheet surface pressing surface 64 a is deformed upward (counterclockwise denoted by the arrow in FIG. 13) in the arrow direction against the biasing spring 64 b. Then, as illustrated in FIG. 13, the sheet surface pressing surface 64 a presses the upper surface of the sheet bundle toward the sheet placing surface 24 a by the action of the biasing spring 64 b.

The thus configured first carry-out member 61 reciprocates with the first carrier member 65 a, and the second carry-out member 63 reciprocates with a second carrier member 65 b between a base end part and an exit end part of the sheet placing surface 24 a. To this end, the sheet placing surface 24 a is provided with drive pulleys 66 a, 66 b and a driven pulley 66 c which are spaced apart from each other by a conveyance stroke. Reference numerals 66 d and 66 e are each an idling pulley.

The first carrier member 65 a (toothed belt in the drawings) is installed between the drive pulley 66 a and the driven pulley 66 c, and the second carrier member 65 b (toothed belt) is installed between the drive pulley 66 b and the driven pulley 66 c through the idling pulleys 66 d, 66 e. A drive motor M4 is connected to the drive pulleys 66 a and 66 b. The first drive pulley 66 a is formed to have a small diameter and the second drive pulley 66 b is formed to have a large diameter so that the rotational force of the drive motor M4 is transmitted to the first carrier member 65 a at a low speed and to the second carrier member 65 b at a high speed.

That is, the first conveying member 60A and the second conveying member 60B are connected in common to the drive motor M4 through a decelerating mechanism (belt pulleys, gear coupling, or the like) so as to travel respectively at a low speed and a high speed. In addition, a cam mechanism is incorporated in the second drive pulley 66 b to delay the drive transmission. This is, as will be described later, because of the difference between the movement stroke Str1 of the first conveying member 60A and the movement stroke Str2 of the second conveying member 60B and positional adjustment of waiting positions of the respective members.

The above cam mechanism will be described with reference to FIGS. 23A to 23C. As described above, rotation of a rotary shaft 67 x of the drive motor M4 is transmitted to the drive pulley 66 a of the first carrier member (first belt) 65 a through a transmitting belt. Accordingly, forward and reverse rotation of the drive motor M4 is transmitted directly to the first belt 65 a. That is, the forward rotation causes the first belt 65 a to travel in a sheet bundle carry-out direction, while the reverse rotation causes the first belt 65 a to travel in a return direction.

Further, the rotational force of the rotary shaft 67 x of the drive motor M4 is transmitted to the drive pulley 66 b of the second carrier member (second belt) 65 b through a transmitting belt. The rotary shaft 67 x is connected to the drive pulley 66 b through transmission cams (a convex cam 67 a and a concave cam 67 b). According to the connection, the rotational force of the rotary shaft 67 x of the drive motor M4 is transmitted to the drive pulley 66 b so as to be delayed by a predetermined angle.

FIG. 23B illustrates a state of activation of the motor rotary shaft 67 x and FIG. 23C illustrates a state after rotation by the predetermined angle. As illustrated in FIGS. 23B and 23C, the convex cam 67 a is integrally formed with the motor rotary shaft 67 x and the concave cam 67 b to be engaged with the convex cam 67 a is formed at the drive pulley 66 b. The convex cam 67 a and the concave cam 67 b form a play angle (η) therebetween so as to be mutually engaged after the rotation by the predetermined angle without being engaged within the range of the predetermined angle.

That is, in the state of activation of the motor rotary shaft 67 x illustrated in FIG. 23B, the convex cam 67 a which rotates in the counterclockwise direction becomes into the state of FIG. 23C after being rotated by the predetermined angle owing to the play angle (η) formed between the convex cam 67 a and the concave cam 67 b. Then, the drive force of the convex cam 67 a is transmitted to the concave cam 67 b to start rotation of the driving pulley 66 b.

Similarly, when the second belt 65 b is to be returned by reverse rotation of the drive motor M4, the second belt 65 b starts traveling with a delay by the predetermined angle (distance) with respect to the first belt 65 a and returns to a position with the delay by the predetermined distance.

Thus, the second conveying member 60B fixed to the second belt 65 b starts driving with a delay by a predetermined time and returns to a position with a delay by a predetermined distance with respect to the first conveying member 60A fixed to the first belt 65 a. Accordingly, the waiting position of the second conveying member 60B can be varied with respect to rotation timing of the drive motor M4. According to the above, the waiting position can be adjusted when the second conveying member 60B is caused to wait at the back face (bottom portion) side of the processing tray 24.

With the above configuration, the first conveying member 60A reciprocates on a linear trajectory with the first stroke Str1 from the rear end regulation position of the processing tray 24, and the first section Tr1 is set within the first stroke Str1. The second conveying member 60B reciprocates on a semi-loop trajectory with the second stroke Str2 from the first section Tr1 to the exit end of the processing tray 24, and the second section Tr2 is set within the second stroke Str2.

The first conveying member 60A is moved downstream from the sheet rear end regulation position (moved from the state illustrated in FIG. 11 to the state illustrated in FIG. 12 at a speed V1 by rotation in one direction of the drive motor M4 to convey the sheet bundle while pushing the rear end thereof with the stop surface 61 a. Being delayed by a predetermined time from the first conveying member 60A, the second conveying member 60B projects above the sheet placing surface 24 a from the waiting position (FIG. 11) on the back surface side of the processing tray 24 and is moved in the same direction at a speed V2 following the first conveying member 60A. Since the speed V2 is set to be higher than the speed V1, the sheet bundle on the processing tray 24 is relayed from the first conveying member 60A to the second conveying member 60B.

FIG. 12 illustrates a state of the relay conveyance. The second conveying member 60B travelling at the speed V2 catches up with the sheet bundle travelling at the speed V1. That is, after passing through the first section Tr1, the second conveying member 60B catches up with the first conveying member 60A and performs conveyance to the downstream side in the second section Tr2 while being engaged with the rear end surface of the sheet bundle.

When the second conveying member 60B abuts, at the relay point at a high speed, against the sheet bundle travelling at the speed V1, the sheet bundle is carried out toward the stack tray 25 while the rear end thereof is held so as to be nipped between the sheet surface pressing member 64 and the carrier member (belt) 65 a (65 b) with the upper surface of the sheet bundle pressed by the sheet surface pressing surface 64 a.

[Next Sheet Front End Guide]

The second conveying member 60B is moved up to the downstream side end portion of the processing tray 24 in the conveying direction to discharge a sheet bundle as described above. During this operation, sheets constituting the next sheet bundle is continuously fed from the image forming apparatus. Thus, there may be a case where the front end of the next sheet enters the processing tray 24 during or immediately after discharge of the preceding sheet bundle toward the stack tray 25, which may make the front end of the next sheet contact the second conveying member 60B, causing a conveyance jam. This inconvenience can be solved by delaying the discharge timing of the next sheet; however, in the image forming system, to prevent a reduction in productivity, the sheet post-processing apparatus preferably receives image-formed sheets from the image forming apparatus without delay so as not to stop a printing operation.

To achieve such a high level of productivity as described above, in the present embodiment, a conveying guide that cooperatively operates with a discharge claw is provided at an upstream location relative to the discharge claw in the conveying direction so as to guide the front end of the next sheet. This allows discharge of the next sheet onto the processing tray to be started in an overlapping manner with the discharge timing of the preceding sheet bundle from the processing tray to the stack tray. Thus, it is possible to receive the next sheet without delay and further to reduce the occurrence of a conveyance jam. In the following, the sheet front end guide will be described in detail.

First Embodiment

A next sheet front end guide 68 according to a first embodiment illustrated on FIGS. 14 and 15 is constituted by a lever having a rotary fulcrum located at the upstream position of a discharge claw 60 b in the conveying direction and is configured to be turnable by its own weight. As illustrated in FIG. 14, the guide 68 contacts the conveying belt 65 b at an end portion thereof on the side opposite to the rotary fulcrum to form a predetermined inclined angle so as to allow the front end of a next sheet S being conveyed to ride over the guide 68. Further, the leading end of the guide 68 is positioned below the sheet placing surface 24 a of the processing tray, preventing the next sheet from being caught with the rear of the discharge claw.

Thus, when the second conveying member 60B is in the state illustrated in FIG. 15 where it is located at the discharge position to discharge a sheet bundle to the stack tray 25, and when the second conveying member 60B in the middle of reciprocating movement (position illustrated in FIG. 14) to return to the waiting position after discharge of the sheet bundle, the guide 68 functions as a conveying surface for the next sheet S delivered from the sheet discharge port 23 by the sheet discharge roller 32 to support discharge of the next sheet S.

Second Embodiment

A next sheet front end guide 168 according to a second embodiment illustrated in FIGS. 16 to 21 will be described. As illustrated in the perspective view of FIG. 16, the next sheet front end guide 168 is constituted by a turnable lever having a rotary fulcrum B arranged at an upstream location relative to a discharge claw 160B in the conveying direction. The next sheet front end guide 168 attached to the discharge claw 160 b is configured to be pressed against the belt 65 b by a twisted coil spring (coil spring SP in FIG. 21) provided at the rotary fulcrum B. Even in a state where the guide 168 is at a waiting position (FIG. 17) and in a state where the guide 168 is being moved, i.e., where the guide 168 passes the position at which the belt 65 b is wound around the pulley (FIG. 18), the guide 168 follows and always contacts the belt 65 b. The guide 168 has a stopper part 168S at its rotary fulcrum side. The stopper part 168S is configured to contact the discharge claw 160B to prevent the guide 168 from rotating by a predetermined or larger angle. Thus, the guide 168 is not lifted above the position at which the stopper part 168S contacts the discharge claw 160B, so that the downstream end of the guide 168 in the conveying direction is further pressed against the belt 65 b at the position where the belt 65 b is linear (as in FIGS. 19 and 20 illustrating a state in the middle of conveyance). The belt 65 b is formed of a flexible material such as rubber, so that the belt 65 b is pressed down by the guide 168 at the position where the belt 65 b is linear, bending the belt 65 b. The belt 65 b is substantially flush with the sheet placing surface 24 a or positioned slightly therebelow, so that in a state where the guide 168 presses down the belt 65 b, the upstream end of the guide 168 in the conveying direction enters below the surface 24 a of the processing tray 24, thereby reducing the occurrence of a conveyance jam due to catching of the front end of the next sheet with the upstream side of the discharge claw in the discharge direction. FIG. 21 illustrates the position at which a sheet is discharged by the discharge claw 160 b in the second embodiment. Even at this position, a roller 168C at the leading end of the guide 168 contacts the belt 65 b to bend the belt 65 b.

Thus, in a state illustrated in FIG. 21 (the second conveying member 160B is located at the discharge position to discharge a sheet bundle to the stack tray 25) and in a state illustrated in FIG. 20 (the second conveying member 160B is in the middle of reciprocating movement to return to the waiting position after discharge of the sheet bundle), the guide 168 functions as a conveying surface for the next sheet S delivered from the sheet discharge port 23 by the sheet discharge roller 32 to support discharge of the next sheet S.

Third Embodiment

A next sheet front end guide 268 according to a third embodiment illustrated in FIG. 22 is mounted on the conveying belt 65 b as with a discharge claw 260 b at a position upstream relative to the discharge claw 260 b in the conveying direction. The conveying guide 268 reciprocates in the sheet conveying direction in conjunction with the discharge claw 260 b but, as illustrated in FIG. 22, stays at a position (linear portion) where it cannot be turned even if the discharge claw 260 b turns at the discharge position to discharge a sheet bundle. The guide surface of the next sheet front end guide 268 is thus not changed in angle so as to be able to guide the next sheet. This prevents a gap into which a sheet can be inserted from being formed upstream of the discharge claw in the conveying direction when the discharge claw 260 b turns and also prevents the sheet front end from being stopped due to abutment against the dis charge claw.

Thus, in a state where the second conveying member 260B is located at the discharge position to discharge a sheet bundle to the stack tray 25 and in a state where the second conveying member 260B is in the middle of reciprocating movement to return to the waiting position after discharge of the sheet bundle, the guide 268 functions as a conveying surface for the next sheet S delivered from the sheet discharge port 23 by the sheet discharge roller 32 to support discharge of the next sheet S.

[Method of Binding Processing (Binding Position)]

As described above, sheets conveyed to the carry-in port 21 of the sheet discharge path 22 are collated and stacked on the processing tray 24 and positioned (aligned) by the sheet end regulating member 40 and side aligning member 46 at the previously set location and in the previously set posture. Thereafter, binding processing is performed for the sheet bundle, and the resultant sheet bundle is discharged onto the stack tray 25 provided at a downstream location. In the following, a method of the binding processing will be described.

In the illustrated example, the processing tray 24 is provided with the “first binding unit 26 for staple binding of a sheet bundle” and the “second binding unit 27 for non-staple binding of a sheet bundle”. The controller 75 to be described later performs binding for a sheet bundle using a selected one of the first and second binding units 26 and 27 and discharges the bound sheet bundle toward a downstream location. This is a first feature of the binding method. Using a staple for binding allows bookbinding to make it difficult for the bound sheets to come off the bundle; however, such convenience that the bound sheets are easily separated from the sheet bundle may be required for some uses. Further, when a used sheet bundle is to be shredded, when sheets are recycled, or the like, the metal staple needs to be removed before the shredding. Thus, it is preferable for a user to be able to select one from “staple binding” and “non-staple binding”.

Further, in addition to a series of post-processing operations including the sheet carry-in from the sheet carry-in path (sheet discharge path) 22, collation/stacking, and binding, it is possible to bind sheets (hereinafter, referred to as “manual stapling processing”) prepared outside the apparatus (outside the system). This is a second feature of the binding method.

To this end, a manual feed setting part 29 having a manual feed setting surface 29 a on which the sheet bundle prepared outside is set is formed in the external casing 20 b, and the abovementioned staple binding unit (stapling unit) 26 is configured to move from a sheet carry-in area Ar of the processing tray 24 to a manual feed area Fr.

Based on FIGS. 8, 9, and 10A to 10C, the binding methods will be individually described. There are defined in this apparatus multi-binding positions Ma1 and Ma2 where sheets are staple-bound at a plurality of positions, corner binding positions Cp1 and Cp2 where sheets are bound at a corner, a manual binding position Mp where binding processing is performed for manually-set sheets, and a non-staple binding position Ep where sheets are bound at a corner without using a staple. In the following, positional relation among the respective binding positions will be described.

Based on FIG. 8, the binding methods will be individually described. There are defined in this apparatus multi-binding positions Ma1 and Ma2 where sheets are staple-bound at a plurality of positions, corner binding positions Cp1 and Cp2 where sheets are bound at a corner, a manual binding position Mp where binding processing is performed for manually set sheets, and a non-staple binding position Ep where sheets are bound at a corner without using a staple. In the following, positional relation among the respective binding positions will be described.

[Multi-Binding]

As illustrated in FIG. 5, in the multi-binding processing, a sheet bundle (hereinafter, referred to as “aligned sheet bundle”) positioned on the processing tray 24 by the sheet end regulating member 41 and side aligning members 46 is bound at the end edge (rear end edge in the drawings). The multi-binding positions Ma1 and Ma2 where binding processing is performed at two distanced positions is defined in FIG. 9. The stapling unit 26 to be described later is moved from a home position to the binding position Ma1 and the binding position Ma2 sequentially in this order and performs binding processing at the binding positions Ma1 and Ma2. Not limited to two positions, the binding processing may be performed at three or more positions as the multi-binding positions Ma. FIG. 24A illustrates a multi-bound state.

[Corner Binding]

For the corner binding processing, there are defined binding positions as two lateral positions being a right corner binding position Cp1 where binding processing is performed at the right corner on an aligned sheet bundle stacked on the processing tray 24 and a left corner binding position Cp2 where binding processing is performed at the left corner of an aligned sheet bundle. In this case, the binding processing is performed with a staple being oblique by a predetermined angle (between about 30° to about 60°). The stapling unit 26 to be described later is mounted on the unit frame with the entire unit being oblique by the predetermined angle thereat. FIGS. 24B and 24C illustrate corner-bound states, respectively.

FIGS. 24B and 24C illustrate a case where the binding processing is performed at either the right corner or left corner of a sheet bundle and a staple is set oblique by the predetermined angle. Not limited to the above, even in a case where binding is performed on only one of the left and right corners, it is also possible to adopt an arrangement that the binding is performed with a staple being parallel to a sheet end edge without being oblique.

[Manual Binding]

The manual binding position Mp is set on the manual feed setting surface 29 a formed in the external casing 20 b (a part of the apparatus housing). The manual feed setting surface 29 a is disposed adjacently in parallel to the sheet placing surface 24 a through the side frame 20 c at a height position substantially flush with the sheet placing surface 24 a of the processing tray 24. In the illustrated example, both the sheet placing surface 24 a of the processing tray 24 and the manual feed setting surface 29 a support a sheet in a substantially horizontal posture and at substantially the same height. FIG. 24D illustrates a manual-bound state.

That is, in FIG. 5, the manual feed setting surface 29 a and the sheet placing surface 24 a are disposed on the right side and left side, respectively, with the side frame 20 c as the boundary. The manual binding position Mp is set on the same line as the abovementioned multi-binding position Ma disposed on the sheet placing surface 24 a. This is for allowing both the multi-binding and manual binding to be performed by the same stapling unit 26. Thus, there are set, on the processing tray 24, the sheet carry-in area Ar, manual feed area Fr (apparatus front side), and eco-binding area Rr (apparatus rear side).

[Non-Staple Binding Position]

The non-staple binding position Ep (hereinafter, referred to as “eco-binding position”) is defined so that binding processing is performed at a side edge part (corner part) of sheets as illustrated in FIG. 5. The illustrated eco-binding position Ep is defined at a position where the binding processing is performed for one position at the side edge part of a sheet bundle in the sheet discharge direction. Then, the binding processing is performed as being oblique to sheets by a predetermined angle. The eco-binding position Ep is defined in the eco-binding area Rr which is situated at the apparatus rear side distanced from the sheet carry-in area Ar of the processing tray 24.

[Mutual Relation Among Binding Positions]

The multi-binding positions Ma1 and Mat are defined within (inside) the sheet carry-in area Ar where sheets are carried in onto the processing tray 24 from the sheet discharge port 23. Each of the corner binding positions Cp1 and CP2 is defined outside the sheet carry-in area Ar at a reference position which is apart rightward or leftward (side alignment reference) by a predetermined distance from the sheet discharge reference Sx (center reference). As illustrated in FIG. 6, at the outer side from a side edge of a maximum size sheet to be bound, the right corner binding position Cp1 is defined at a position deviated rightward from one side edge of the sheet by a predetermined amount (δ1) and the left corner binding position Cp2 is defined at a position deviated leftward from the other side edge of the sheet by a predetermined amount (δ2). The deviation amounts are set to be the same (δ1=δ2).

The multi-binding positions Ma1, Mat and manual binding position Mp are defined approximately on the same straight line. Further, the corner binding positions Cp1, Cp2 are defined at positions each having an oblique angle (e.g., 45°) to be laterally symmetric with respect to the sheet discharge reference Sx.

The manual binding position Mp is defined in the manual feed area Fr in the apparatus front side Fr and outside the sheet carry-in area Ar. The eco-binding position Ep is defined in the eco-binding area Rr at the apparatus rear side Re and outside the sheet carry-in area Ar.

Further, the manual binding position Mp is defined at a position which is offset by a predetermined amount (Of1) from the right corner binding position Cp1 of the processing tray 24. The eco-binding position Ep is defined at a position which is offset by a predetermined amount (Of2) from the left corner binding position Cp2 of the processing tray 24. Thus, the multi-binding positions Ma are defined based on the sheet carry out reference (center reference) of the processing tray 24 to which sheets are carried in, and the corner binding positions Cp1 and Cp2 are defined based on the maximum sheet size. Further, the manual binding position Mp is defined at the position which is offset by the predetermined amount (Of1) from the right corner binding position Cp1 to the apparatus front side. Similarly, the eco-binding position Ep is defined at the position which is offset by the predetermined amount (Of2) from the left corner binding position Cp2 to the apparatus rear side. According to the above, arrangement can be made in an orderly manner without causing interference of sheet movement.

The sheet movement in each binding processing will be described. In the multi-binding processing, sheets are carried in onto the processing tray 24 in center reference (or side reference) and aligned in this state, and then subjected to the binding processing. After the binding processing is performed, the sheets are discharged downstream in the above posture. In the corner binding processing, sheets are aligned at the alignment position on a designated side and subjected to the binding processing. After the binding processing is performed, the sheets are discharged downstream in the above posture. In the eco-binding processing, the sheets carried in onto the processing tray 24 are offset by the predetermined amount Oft to the apparatus rear side after being stacked into a bundle shape and are subjected to the binding processing after the offset movement. After the binding processing, the resultant sheet bundle is offset by a predetermined amount (for example, being the same as or smaller than the offset Oft) to the sheet center side and discharged downstream thereafter.

Further, in the manual binding, an operator sets sheets on the manual feed setting surface 29 a distanced by the predetermined amount Of1 from the alignment reference which is positioned at the front side from the processing tray 24. This allows a plurality of the binding processing to be performed while sheet setting positions therefor are defined in the direction perpendicular to the sheet conveying direction. Therefore, sheet jamming can be suppressed while keeping high processing speed.

In the eco-binding processing, the controller 75 to be described later defines the eco-binding position Ep with sheets offset by a predetermined amount Of3 in the sheet discharge direction from the rear end reference position. This is to avoid interference between the stapling unit 26 for the left corner binding and the eco-binding unit (press binding unit 27 to be described later). Thus, if the eco-binding unit 27 is movably mounted on the apparatus housing 20 between the binding position and a retracting position retracting therefrom similarly to the stapling unit 26, the sheets need not be offset by the amount Of3 in the sheet discharge direction.

Here, the apparatus front side Fr refers to the front side of the external casing 20 b set in apparatus designing where various kinds of operation are performed by an operator. Normally, a control panel, a mount cover (door) for a sheet cassette, and an open-close cover through which staples are replenished for a stapling unit are arranged at this apparatus front side. Further, the apparatus rear side Re refers to the side of the apparatus facing a wall surface of a building, for example, when the apparatus is installed (installation conditions; the back surface is designed to face a wall).

Thus, in the illustrated apparatus, the manual binding position Mp is defined on the apparatus front side Fr, and the eco-binding position Ep is defined on the apparatus rear side Re outside the sheet carry-in area Ar with reference thereto. A distance Ofx between the manual binding position Mp and the reference of the sheet carry-in area Ar (sheet carry-in reference Sx) is set larger than a distance Ofy between the sheet carry-in reference Sx and the eco-binding position Ep (i.e., Ofx>Ofy).

Thus, the manual binding position Mp is defined to be apart from the sheet carry-in reference Sx of the processing tray 24 and the eco-binding position Ep is defined to be close to the sheet carry-in reference Sx. This is because the operation of setting a sheet bundle to the manual binding position Mp from the outside is facilitated to be convenient owing to that the manual binding position Mp is distanced from the processing tray 24. Further, the eco-binding position Ep is defined to be close to the sheet carry-in reference Sx. This is because the movement amount when sheets (an aligned sheet bundle) carried in onto the processing tray 24 are offset-moved to the eco-binding position Ep can be small for speedy performance of the binding processing (i.e., improvement in productivity).

[Moving Mechanism for Stapling Unit]

Although a detailed structure will be described later, the stapling unit 26 (first binding unit) includes a unit frame 26 a (first unit frame), a staple cartridge 39, a stapling head 26 b, and an anvil member 26 c. The stapling unit 26 is supported by the apparatus frame 20 a to reciprocate by a predetermined stroke along a sheet end surface on the processing tray 24. The following describes the supporting structure.

FIG. 7 illustrates a structure as viewed from the front side, in which the stapling unit 26 is attached to the apparatus frame 20 a, and FIG. 8 is a plan view thereof. FIGS. 9 and 10 are partial explanatory views of a guide rail mechanism for guiding the stapling unit 26.

As illustrated in FIG. 7, a chassis frame (hereinafter, referred to as “bottom frame”) 20 e is attached to the right and left side frames 20 c and 20 d constituting the apparatus frame 20 a. The stapling unit 26 is mounted on the bottom frame 20 e so as to be movable by a predetermined stroke. The bottom frame 20 e is further provided with a travel guide rail (hereinafter, referred to simply as “guide rail”) 42 and a slide cam 43. The guide rail 42 has a travel rail surface 42 x, and the slide cam 43 has a travel cam surface 43 x. In cooperation with each other, the travel rail surface 42 x and the travel cam surface 43 x cooperatively support the stapling unit 26 (hereinafter, referred to as “moving unit” in this section) so as to allow the moving unit to reciprocate by the predetermined stroke and to control the angular posture thereof.

The travel rail surface 42 x and the travel cam surface 43 x are formed so that the travel guide rail 42 and the slide cam 43 allow the moving unit 26 to reciprocate within a movement range SL (sheet carry-in area Ar, manual feed area Fr, and the eco-binding area Rr) (see FIG. 8). The travel guide rail 42 is constituted by a rail member having the stroke SL along the rear end regulating member 41 of the processing tray 24. In the illustrated example, the travel guide rail 42 is constituted as an opening groove formed in the bottom frame 20 e. The travel rail surface 42 x is formed at the edge of the opening and is arranged on the same straight line as the rear end regulating member 41 of the processing tray 24 as being in parallel thereto. The slide cam 43 is disposed distanced from the travel rail surface 42 x. In the illustrated example, the slide cam 43 is constituted by a groove cam formed in the bottom frame 20 e. The groove cam has the travel cam surface 43 x.

A drive belt 44 connected to a drive motor (travel motor) M11 is fixed to the moving unit (stapling unit) 26. The drive belt 44 is wound around a pair of pulleys axially supported by the apparatus frame 20 e, and the drive motor is connected to one of the pulleys. Thus, the stapling unit 26 reciprocates by the stroke SL with forward and reverse rotation of the travel motor M11.

The travel rail surface and travel cam surface are arranged to include parallel interval sections 43 a, 43 b (having a span G1) where the surfaces are in parallel, a narrow swing interval sections 43 c, 43 d (having a span G2), and a narrower swing interval section 43 e (having a span G3) (span G1>span G2>span G3). The span G1 causes the stapling unit to be in a posture parallel to the sheet rear end edge. The span G2 causes the stapling unit to be in a slant posture rightward or leftward. The span G3 causes the stapling unit to be in a posture slant at a larger angle. Thus, the slant angle of the stapling unit is varied.

Not limited to the opening groove structure, the travel guide rail 42 may adopt a variety of structures such as a guide rod, a projection rib, and others. Further, not limited to the groove cam, the slide cam 43 may adopt a variety of shapes as long as it has a cam surface to guide the moving unit 26 in a predetermined stroke direction, such as a projection stripe rib member.

The moving unit 26 is engaged with the travel guide rail 42 and the slide cam 43 as follows. As illustrated in FIG. 7, the moving unit 26 is provided with a first rolling roller (rail fitting member) 50 to be engaged with the travel rail surface 42 x and a second rolling roller (cam follower member) 51 to be engaged with the travel cam surface 43 x. Further, the moving unit 26 is provided with a sliding roller 52 to be engaged with a support surface of the bottom frame 20 e. The illustrated moving unit 26 includes two ball-shaped sliding rollers, 52 a and 52 b at two positions thereof. Further, a guide roller 53 to be engaged with the bottom surface of the bottom frame 20 e is formed in the moving unit 26 to prevent the moving unit 26 from floating from the bottom frame 20 e.

With the above configuration, the moving unit 26 is movably supported by the bottom frame 20 e through the sliding rollers 52 a, 52 b and the guide roller 53. Further, the first rolling roller 50 and the second rolling roller 51 are rotated and moved along the travel rail surface 42 x and the travel cam surface 43 x, respectively, so as to follow the travel rail surface 42 x and the travel cam surface 43 x, respectively.

The travel rail surface 42 x and the travel cam surface 43 x are arranged so that the parallel distance sections (span G1) are arranged at the position 43 a corresponding to the abovementioned multi-binding positions Ma1, Ma2 and the position 43 b corresponding to the manual binding position Mp. With the span G1, the moving unit 26 is maintained in a posture perpendicular to the sheet end edge without swinging, as illustrated in FIGS. 9A and 10C. Accordingly, at the multi-binding positions Ma1, Ma2 and the manual binding position Mp, a sheet bundle is bound with a staple being in parallel to the sheet end edge.

Further, the travel rail surface 42 x and the travel cam surface 43 x are arranged so that the swing distance sections (span G2) are arranged at the position 43 e corresponding to the right corner binding position and the position 43 d corresponding to the left corner binding position. The moving unit 26 is maintained in a rightward-angled posture (for example, rightward-angled by 45°) or in a leftward-angled posture (for example, leftward-angled by 45°), as illustrated in FIGS. 9A and 10A.

Further, the travel rail surface 42 x and the travel cam surface 43 x are arranged so that the swing distance section (span G3) is arranged at the position 43 c facing a position for staple loading. The span G3 is formed to be smaller than the span G2. In this state, the moving unit 26 is maintained in a rightward-angled posture (for example, rightward-angled by 60°) as illustrated in FIG. 10B. The reason why the angular posture of the moving unit 26 is changed at the staple loading position is that the posture matches an angular direction in which the staple cartridge 39 is mounted thereon. The angle is set in relation with the open-close cover arranged at the external casing 20 b.

For changing the angular posture of the moving unit 26 using the travel rail surface 42 x and the travel cam surface 43 x, it is preferable, from a viewpoint of compactness in layout (to reduce a movement length), to arrange a second travel cam surface or a stopper cam surface for an angle change in cooperation with the travel cam surface 43 x.

The illustrated stopper cam surface will be described. As illustrated in FIG. 8, stopper surfaces 43 y and 43 z to be engaged with a part of the moving unit 26 (sliding roller 52 a) are arranged at the bottom frame 20 e to change the posture of the moving unit 26 between the right corner binding position Cp1 and the manual binding position Mp on the apparatus front side. Thus, the moving unit 26 inclined at the staple loading position is required to be corrected in inclination at the manual binding position Mp; however, when the angle is changed only by the cam surface and rail surface, the movement stroke becomes long.

Thus, when the moving unit 26 is moved toward the manual binding position Mp in a state of being locked by the stopper surface 43 y, the inclination of the moving unit 26 is corrected to become the original state. Further, when the moving unit 26 is returned to the opposite direction from the manual binding position Mp, the moving unit 26 is (forcedly) inclined to face the corner binding position Cp1 by the stopper surface 43 z.

[Stapling Unit]

The stapling unit 26 has widely been known as means for performing binding processing using a staple. An example thereof will be described with reference to FIG. 25A. The stapling unit 26 is configured as a unit separate from the sheet bundle binding apparatus (post-processing apparatus B). The stapling unit 26 includes a box-shaped unit frame 26 a, a drive cam 26 d axially swingably supported by the unit frame 26 a, and a drive motor M8 mounted on the unit frame 26 a to rotate the drive cam 26 d.

On the drive cam 26 d the stapling head 26 b and the anvil member 26 c are arranged at a binding position so as to be mutually opposed. The stapling head 26 b is vertically moved between a waiting position on the upper side and a stapling position (the anvil member 26 c) on the lower side with the drive cam 26 d and a biasing spring (not illustrated). Further, the staple cartridge 39 is mounted on the unit frame 26 a in a detachably attachable manner.

Linear blank staples are stored in the staple cartridge 39 and fed to the stapling head 26 b by a staple feeding mechanism. The stapling head 26 b incorporates a former member to fold a linear staple inward into a U-shape and a driver to cause the folded staple to bite into a sheet bundle. With such a configuration, the drive cam 26 d is rotated by the drive motor M8 to store energy in the biasing spring. When the rotational angle reaches a predetermined angle, the stapling head 26 b is vigorously lowered toward the anvil member 26 c. Owing to this action, a staple is caused to bite into a sheet bundle with the driver after being folded into a U-shape. Then, the leading ends of the staple are folded by the anvil member 26 c, whereby staple binding is completed.

The staple feeding mechanism is incorporated in between the staple cartridge 39 and the stapling head 26 b. A sensor (empty sensor) to detect the absence of the staple is arranged in the staple feeding mechanism. Further, the unit frame 26 a has a cartridge sensor (not illustrated) to detect whether or not the staple cartridge 39 has been inserted.

The illustrated staple cartridge 39 adopts a structure in which the staples connected in a belt shape are stacked in a layered manner or are stored in a roll-shape in a box-shaped cartridge.

Further, the unit frame 26 a has a circuit to control the abovementioned sensors and a circuit board to control the drive motor M8, and an alarm signal is issued when the staple cartridge 39 is not mounted or the staple cartridge 39 is empty. Further, the stapling control circuit controls the drive motor M8 to perform the stapling operation with a staple signal and transmits an “operation completion signal” when the stapling head 26 b is moved to an anvil position from the waiting position and returned to the waiting position.

[Press Binding Unit]

The structure of the press binding unit 27 will be described based on FIG. 25B. As a press binding mechanism, there have been known a fold-binding mechanism (see JP 2011-256008A) to perform binding by forming cutout openings in a binding portion of a plurality of sheets and mating by folding a side of each sheet and a press binding mechanism to perform binding by pressing and deforming a sheet bundle with corrugated surfaces formed on pressurizing surfaces 27 b and 27 c which are capable of freely pressure-contacting and separating from each other.

FIG. 25B illustrates the press binding unit 27. A movable frame member 27 d is swingably axially supported by a base frame member 27 a, and both the frame members are swung about a support shaft 27 x so as to be capable of pressure-contacting and separating from each other. The movable frame member 27 b has a follower roller 27 f with which a drive cam 27 e arranged at the base frame member 27 a is engaged.

A drive motor M9 arranged at the base frame member 27 a is connected to the drive cam 27 e through a deceleration mechanism. Rotation of the drive motor M9 causes the drive cam 27 e to be rotated, and the movable frame member 27 d is swung by a cam surface (eccentric cam in the drawing) thereof.

The lower pressurizing surface 27 c and the upper pressurizing surface 27 b are arranged respectively at the base frame member 27 a and the movable frame member 27 d so as to be opposed to each other. A biasing spring (not illustrated) is arranged between the base frame member 27 a and the movable frame member 27 d to bias both the pressurizing surfaces in a direction to be separated.

As illustrated in an enlarged view of FIG. 25B, convex stripes are formed on one of the upper pressurizing surface 27 b and the lower pressurizing surface 27 c and concave grooves to be matched therewith are formed on the other thereof. The convex stripes and the concave grooves are each formed into a rib-shape having a predetermined length. Sheets of a sheet bundle nipped between the upper pressuring surface 27 b and the lower pressurizing surface 27 c are deformed into a corrugation shape to closely adhere to one another. A position sensor (not illustrated) is arranged at the base frame member (unit frame) 27 a and detects whether or not the upper and lower pressurizing surfaces 27 b and 27 c are at the pressurization positions or separated positions.

[Stack Tray]

The structure of the stack tray 25 will be described based on FIG. 26. The stack tray 25 is disposed downstream from the processing tray 24 and stacks and stores thereon a sheet bundle discharged from the processing tray 24. A tray elevating mechanism is provided so that the stack tray 25 is sequentially lowered in accordance with a stacked amount thereon. The height of the stack surface of the stack tray 25 (the uppermost level of sheets) is controlled so that the uppermost sheet thereon is to be approximately flush with the sheet placing surface of the processing tray 24. Further, stacked sheets are inclined by an angle with a rear end edge in the sheet discharge direction abutting against a tray aligning surface 20 f (standing surface) by their own weight.

Specifically, an elevating rail 54 is vertically fixed in the stacking direction to the apparatus frame 20 a. A tray base body 25 x is slidably fitted to the elevating rail 54 so as to be capable of being elevated and lowered using a slide roller 55 or the like. A rack 25 r is formed in the elevating direction integrally with the tray base body 25 x. A drive pinion 56 axially supported by the apparatus frame 20 a is engaged with the rack 25 r. Then, an elevating motor M10 is connected to the drive pinion 56 through a worm gear 57 and a worm wheel 58.

Accordingly, when the elevation motor M10 is rotated forwardly and reversely, the rack 25 r connected to the drive pinion 56 is vertically moved to the upper side and lower side of the apparatus frame 20 a. With the above configuration, the tray base body 25 x is elevated in a cantilevered state. In addition to such a rack-pinion mechanism, the tray elevating mechanism may adopt a pulley-mounted belt mechanism or the like.

The stack tray 25 is integrally attached to the tray base body 25 x. Sheets are stacked and stored on the stack surface 25 a thereof. The tray aligning surface 20 f to support sheet rear end edges is vertically formed in the sheet stacking direction. In the illustrated example, the tray aligning surface 20 f is formed with the external casing.

Further, the stack tray 25 integrally attached to the tray base body 25 x is arranged so as to be inclined in an illustrated angled direction. The angle (for example, 20° to 60°) is set so that a sheet abuts at the rear end thereof against the tray aligning surface 20 f by its own weight.

[Sheet Holding Mechanism]

The stack tray 25 has a sheet holding mechanism 53 to press the uppermost stacked sheet. The illustrated sheet holding mechanism includes an elastic pressing member 53 a to press the uppermost sheet, an axially supporting member 53 b to cause the elastic pressing member 53 a to be rotatably axially supported by the apparatus frame 20 a, a drive motor M2 to rotate the axially supporting member 53 b by a predetermined angle, and a transmitting mechanism thereof. The illustrated drive motor M2 is drive-connected to the drive motor of the sheet bundle carry-out mechanism as a drive source. When a sheet bundle is carried in (carried out) to the stack tray 25, the elastic pressing member 53 a is retracted outside the stack tray 25. After the rear end of the sheet bundle is stored on the uppermost sheet on the stack tray 25, the elastic pressing member 53 a is rotated counterclockwise from the waiting position and engaged with the uppermost sheet to press the same.

Then, owing to an initial rotational operation of the drive motor M2 to carry out a sheet bundle on the processing tray 24 toward the stack tray 25, the elastic pressing member 53 a is retracted from the sheet surface of the upmost sheet on the stack tray 25 to the retracting position.

[Level Sensor]

The stack tray 25 has a level sensor to detect a sheet height of the uppermost sheet. The elevating motor M10 is rotated based on a detection signal from the level sensor, so that the stack surface 25 a is lifted. A variety of mechanisms are known as the level sensor mechanism. In the illustrated example, the level sensor mechanism adopts a detection method to detect whether or not a sheet exists at the height position by emitting a detection light from the tray aligning surface 20 f of the apparatus frame 20 a to the tray upper side to detect a reflection light thereof.

[Stack Sheet Amount Sensor]

As with the level sensor, a sensor to detect removal of sheets from the stack tray 25 is arranged at the stack tray 25. Although the structure thereof that is generally adopted will not be described in detail, it is possible to detect whether or not sheets exist on the stack surface, for example, by arranging a sensor lever which is configured to rotate integrally with the elastic pressing member 53 a and detecting the sensor lever with a sensor element. When the height position of the sensor lever becomes different (varied) before and after carry-out of a sheet bundle, the controller 75 to be described later stops the sheet discharge operation or lifts the stack tray 25 to a predetermined position, for example. Such an operation is performed in an abnormal case, for example, in a case where a user carelessly removes sheets from the stack tray 25 during an operation. Further, a lower limit position is defined for the stack tray 25, so as to prevent the stack tray 25 from lowering abnormally. A limit sensor Se3 to detect the stack tray 25 is arranged at the lower limit position.

[Guide Operation of Next Sheet Front End Guide]

As for the embodiments of the above-mentioned next sheet front end guides 68, 168, and 268, the operation and control that is performed after sheet discharge to the stack tray 25 in particular will be described. As described above, the next sheet front end guide is provided to prevent a sheet to be subsequently fed onto the processing tray 24 after the preceding sheet is discharged from the processing tray 24 to the stack tray 25 from accidentally contacting, at its front end, the back side of the sheet bundle carry-out unit 60 (second conveying member 60B, 160B, or 260B) to cause a conveyance jam or sheet damage. The use of the guide surface of the next sheet front end guide can also reduce occurrence of a sheet jam caused due to curling of the front end of a sheet to be fed onto the processing tray 24. In the following, embodiments to positively support the front end of the next sheet will be described.

The sheet to be fed onto the processing tray 24 is delivered by the sheet discharge roller 32 without being nipped at its front end, so that the sheet front end may be curled or hang down, depending on conditions such as sheet size, sheet basis weight, and sheet hardness (rigidity). This becomes prominent particularly when a level difference between the sheet placing surface of the processing tray 24 and the discharge port (sheet discharge roller 32) is large. The following describes an operation for solving problems such as a conveyance jam. Hereinafter, with reference to the flowchart of FIG. 27, an operation flow depending on difference in sheet size will be described.

[Operation Depending on Difference in Sheet Size]

After completion of the discharge operation of a preceding sheet bundle by the sheet bundle carry-out unit 60 (second conveying member 60B, 160B, or 260B), it is recognized, based on information received from the image forming apparatus 1 or a detection result from the entrance sensor Se1, whether or not succeeding sheets are to be carried in (St100, FIG. 27). Then, the controller 75 recognizes the information from the image forming apparatus 1 to check whether the length of the succeeding sheets in the conveying direction is equal to or more than a predetermined length (in the present embodiment, 216 mm), which is determined based on the orientation (vertical or horizontal) of the sheet in addition to the sheet size information (St101). When the sheet size is equal to or more than a predetermined value, the front end of the sheet being delivered onto the processing tray 24 may often be in a free state, so that buckling or curling is highly likely to occur. Thus, the second conveying member 60B (or 160B, 260B) is made to wait at the discharge position of the preceding sheet bundle to the stack tray 25, and then the next sheet is carried in (St 104, FIG. 21).

The second conveying member 60B (or 160B, 260B) is made to stay until the elapse of an estimated time taken for the front end of the next sheet, which is conveyed by the sheet discharge roller 32, contacts the next sheet front end guide 68 (or 168, 268) on the back side of the second conveying member 60B (or 160B, 260B). After the elapse of the estimated time, the sheet bundle carry-out unit 60 is returned to its home position (waiting position) by the time when the next sheet is completely discharged onto the processing tray 24.

On the other hand, when the length of the next sheet in the conveying direction is equal to less than the predetermined length, i.e., when the sheet size is less than the predetermined value (St101), the second conveying member 60B (or 160B, 260B) is retracted to the home position (waiting position) immediately after completion of the discharge (St103). When the sheet length in the conveying direction is small, the front end of the next sheet is less likely to hang down, and a buckling portion is small (if occurred), so that a conveyance jam is less likely to occur. Further, since a time period taken for sheet discharge is small (sheet discharge interval is small), it is necessary to return the second conveying member 60B (or 160B, 260B) to the waiting position earlier. Furthermore, it is preferable for the next sheet front end guide 68 (or 168, 268) not to contact the print surface of the sheet as much as possible for suppressing sheet damage. For the above reasons, the second conveying member 60B (or 160B, 260B) is retracted immediately, followed by carry-in of the next sheet (St105).

After the second conveying member 60B (or 160B, 260B) is moved to the waiting position (St106), the sheet aligning operation is performed (St107). Then, it is checked, based on information received from the image forming apparatus 1 or a detection result from the entrance sensor Se1, whether or not there are succeeding sheets, and the sheets are sequentially received if exist (St108 to St111). Subsequently, the next sheet bundle is aligned by the aligning member 45 (St112) and discharged by the sheet bundle carry-out unit 60 (St113). Then, when it is determined that there are no succeeding sheets (St100), the second conveying member 60B (or 160B, 260B) is moved to the waiting position (St114), and this routine is ended.

With the above processing flow, it is possible to achieve an optimum operation according to sheet size to thereby reduce the occurrence of a conveyance jam without lowering the productivity and to prevent deterioration in print quality.

[Operation Depending on Difference in Sheet Basis Weight]

The following describes an operation flow depending on difference in sheet basis weight with reference to the flowchart of FIG. 28.

After completion of discharge operation of a preceding sheet bundle by the second conveying member 60B (or 160B, 260B), it is recognized, based on information received from the image forming apparatus 1 or a detection result from the entrance sensor Se1, whether or not succeeding sheets are carried in (St200). Then, it is checked, based on information received from the image forming apparatus, whether or not the basis weight of the sheet is less than a predetermined value (recognized by the controller 75) (St201). When the basis weight of the sheet is less than the predetermined value (less than 105 g/m²), it is difficult to impart stiffness to the front end of the sheet being delivered onto the processing tray 24, making it likely to cause buckling or curling, so that the second conveying member 60B (or 160B, 260B) is made to wait at the discharge position of the preceding sheet bundle to the stack tray 25, and the next sheet starts to be discharged by the sheet discharge roller 32 and carried in onto the processing tray 24 (St204) (FIG. 21).

The second conveying member 60B (or 160B, 260B) is made to stay until the elapse of an estimation time taken for the front end of the next sheet, which is conveyed by the sheet discharge roller 32, contacts the next sheet front end guide 268 (until a pulse count for the conveying roller 32 reaches a predetermined value). After the elapse of the estimated time, the second conveying member 60B (or 160B, 260B) is returned to its home position (waiting position, FIG. 11) by the time when the next sheet is completely discharged onto the processing tray 24.

On the other hand, when the basis weight of the next sheet is equal to or more than a predetermined value (exceeding 106 g/m²) (St201), the second conveying member 60B (or 160B, 260B) starts retracting to the home position (waiting position, FIG. 11) (St203). When the sheet basis weight is large, the sheet itself has a sufficient hardness and the front end of the next sheet is less likely to hang down and to be subjected to buckling, so that a conveyance jam is less likely to occur. Further, it is preferable for the next sheet front end guide 68 (or 168, 268) not to contact the print surface (lower surface because of face-down printing) of the sheet as much as possible for maintaining a high level of print quality. For the above reasons, the second conveying member 60B (or 160B, 260B) is retracted immediately after discharge of the preceding sheet bundle, followed by carry-in of the next sheet (St205).

After the second conveying member 60B (or 160B, 260B) is moved to the waiting position (FIG. 11) (St206), the sheet aligning operation is performed by the sheet aligning member 45 (St207). Then, it is checked whether or not there are succeeding sheets, and the sheets are sequentially received if exist (St208 to St211). Subsequently, the next sheet bundle is aligned (St212) and discharged (St213). Then, when it is determined that there are no succeeding sheets (St200), the sheet bundle carry-out unit 60 is moved to the waiting position (St214), and this routine is ended.

As described above, by changing the time period during which the sheet bundle carry-out unit 60 stays at the discharge completion position depending on various sheet conditions, it is possible to reduce the occurrence of a conveyance jam to thereby achieve stable conveying operation.

In addition to the above two embodiments, the following operations are possible. For example, when it is determined based on information related to rigidity that the sheet to be carried in has a low rigidity, the sheet bundle carry-out unit may be made to stay at the discharge position so as to support the front end of the next sheet. In addition, a stop time period during which the sheet bundle carry-out unit may be changed according to information provided for each sheet type. Moreover, a member to support the front end of the next sheet may be changed or a plurality of members may be used to support the front end of the next sheet in a combined manner depending on the printed area or printed location. Furthermore, various kinds of sheet information may be combined for complex determination.

[Difference Depending on Presence or Absence of Shift Operation]

The above description has been made on operations in the straight discharge mode in which the sheet conveyance interval is small in particular. In addition, the stop time period of the discharge claw 60 can be changed depending on the processing mode. For example, there is provided a shift mode in which the aligning member 45 is used to shift a sheet conveyed onto the processing tray 24 in a sheet width direction perpendicular to the conveying direction. In this shift mode, the aligning member 45 (at least one of the side aligning members 46F and 46R) enters the center position at which a sheet conveyed from the discharge port is located (see FIGS. 30 and 31B). Thus, When the next sheet is carried in onto the processing tray 24 in this state, the front end thereof can be supported by the aligning member 45 (at least one of the side aligning members 46F and 46R). The following describes the operation after sheet discharge in the shift mode.

The description will be given with reference to the flowchart of FIG. 29. A preceding sheet bundle that has been shifted is discharged by the second conveying member 60B (or 160B, 260B). After that, it is checked whether or not there are succeeding sheets (St300). Then, the controller 75 recognizes, based on information received from the image forming apparatus 1, whether the succeeding sheets are subjected to straight discharge or shift discharge (St301). When the result of the recognition indicates the straight discharge, the aligning member 45 is moved to the next sheet receiving position (St302), while the second conveying member 60B (or 160B, 260B) is made to stay at the position to discharge the preceding sheet bundle (St304) (see FIGS. 21 and 31A). In this state, the next sheet is carried in (St306), and after elapse of an estimated time taken for the front end of the next sheet passes over the next sheet front end guide 68 (or 168, 268) of the second conveying member 60B (or 160B, 260B) (St308), the second conveying member 60B (or 160B, 260B) is returned to the waiting position (FIG. 11) (St310).

The following describes a case where the succeeding sheets are also subjected to the shift discharge. When there are succeeding sheets (St300), and the next sheet is subjected to the shift discharge (St301), the aligning member 45 (at least one of the side aligning members 46F and 46R) is made to wait at the position at which the preceding sheet bundle is shifted and discharged until the next sheet is discharged (St303, FIGS. 30 and 31B). After that, the second conveying member 60B (or 160B, 260B) is returned to the waiting position (St305). Subsequently, the next sheet is carried in onto the processing tray 24 (St307), and after the elapse of an estimated time taken for the front end of the next sheet passes above the aligning member 45 (at least one of the side aligning members 46F and 46R) (St309), the aligning member 45 (at least one of the side aligning members 46F and 46R) is moved to the sheet receiving position (moved so as to increase the interval between the side aligning members in the sheet width direction) (St311), and the next sheet is positioned on the processing tray 24.

After the next sheet receiving operation in each of the above modes, the aligning member 45 is used for sheet aligning operation (St312), and after completion of the reception of the succeeding sheets, the side aligning member 45 is used to perform sheet aligning and sheet discharge onto the stack tray 25 (St313 to St318). When there are succeeding sheets, operations up to this step is repeatedly executed (St300). When there is no succeeding sheet, the aligning member 45 is returned to the home position (St319), and the sheet bundle carry-out unit 60 (second conveying member 60B, 160B, or 260B) is also moved to the home position (St320). This routine is thus completed.

As described above, in the present embodiment, when the preceding sheet is subjected to the shift job (at least one of the side aligning members 46F and 46R is at the position where it can support the next sheet), and the succeeding sheets are also subjected to the shift job, the aligning member 45 (at least one of the side aligning members 46F and 46R) is made to stay at the shifted position so as to support the front end of the next sheet at its upper portion, while the second conveying member 60B (or 160B, 260B) is moved to the waiting position. When the succeeding sheets are subjected to the straight discharge, the aligning member is moved to the waiting position, and the next sheet front end guide 68 (or 168, 268) of the second conveying member 60B (or 160B, 260B) is used to support the front end of the next sheet. Thus, it is possible to perform an operation that least affects the sheet print surface according to the operation mode of each job and to suppress dirt on the sheet, thereby providing a sheet processing apparatus having high print quality.

In the above description, either one of the second conveying member 60B (or 160B, 260B) and aligning member 45 is used; alternatively, when many images are printed on the print surface of the sheet, and it is thus necessary to distribute a load caused due to contact with the print surface, or when a sheet having extremely low rigidity, such as a thin film or a plastic sheet that is easily bent is used, the above two members may be used in combination.

Further, based on the pulse count for the sheet discharge roller 32, the conveying speed of the sheet discharge roller 32 may be reduced at or before the timing when the front end of the next sheet contacts the next sheet front end guide 68 (or 168, 268) and aligning member 45 and then increased, whereby damage on the sheet can further be reduced.

While the present invention has been described in detail in connection to the preferred embodiments thereof, it should be understood that the present invention is not limited to the above embodiment but various modification or changes may be made within the technical scope of the invention.

This application claims priority from Japanese Patent Application No. 2020-214500 and Japanese Patent Application No. 2020-214501 incorporated herein by reference. 

1. A sheet processing apparatus comprising: a conveying unit that conveys a sheet in a predetermined conveying direction; a processing tray on which the sheet conveyed by the conveying unit is placed; a discharge unit that discharges the sheet placed on the processing tray by pushing a rear end portion of the sheet in the sheet conveying direction; a stack tray on which the sheet discharged by the discharge unit is placed; an aligning unit that aligns the sheet on the processing tray in a sheet width direction perpendicular to the conveying direction; a first support guide integrally provided at an upstream end portion of the discharge unit in the conveying direction and configured to support a downstream front end portion in the conveying direction of a sheet to be conveyed onto the processing tray; and a controller that controls the discharge unit and aligning unit, wherein the controller controls, after a sheet is discharged from the processing tray to the stack tray, the first support guide to support the downstream front end portion in the conveying direction of a next sheet to convey the sheet onto the processing tray.
 2. The sheet processing apparatus according to claim 1, wherein the discharge unit is configured to reciprocate between a waiting position not to contact the sheet on the processing tray and a discharge position to discharge the sheet on the processing tray to the stack tray, and the controller controls the discharge unit to return to the waiting position at a first timing after it reaches the discharge position, when the size of the sheet is equal to or more than a predetermined value, and controls the discharge unit to return to the waiting position at a second timing later than the first timing after it reaches the discharge position, when the size of the sheet is less than a predetermined value.
 3. The sheet processing apparatus according to claim 1, wherein in a shift mode to shift the sheet placed on the processing tray with the aligning unit in the width direction by a predetermined distance, the controller controls, after a sheet is discharged from the processing tray to the stack tray, the second support guide to support the downstream front end portion in the conveying direction of a next sheet to convey the sheet onto the processing tray, and in a straight discharge mode to discharge the sheet placed on the processing tray to the stack tray without shifting the sheet, the controller controls, after a sheet is discharged from the processing tray to the stack tray, the first support guide to support the downstream front end portion in the conveying direction of a next sheet to be conveyed onto the processing tray.
 4. The sheet processing apparatus according to claim 3, wherein the discharge unit is configured to reciprocate between a waiting position not to contact the sheet on the processing tray and a discharge position to discharge the sheet on the processing tray to the stack tray, and the controller controls the discharge unit to return to the waiting position at a first timing after it reaches the discharge position, when the basis weight of the sheet is equal to or more than a predetermined value, and controls the discharge unit to return to the waiting position at a second timing later than the first timing after it reaches the discharge position, when the basis weight of the sheet is less than a predetermined value.
 5. The sheet processing apparatus according to claim 3, further comprising a conveying detection unit that detects a sheet conveying amount by the sheet conveying unit, wherein the controller sets, based on the conveying amount detected by the conveying detection unit, the second timing to an estimated time point or later at which, after the discharge unit reaches the discharge position, the downstream front end portion in the conveying direction of a next sheet to be discharged onto the processing tray reaches the first support guide.
 6. The sheet processing apparatus according to claim 4, wherein the discharge unit includes a first discharge claw that moves within a first section in the conveying direction and a second discharge claw configured to be movable at the downstream side of the first section in the conveying direction by the same drive source as that for the first discharge claw, and the first support guide is provided on the second discharge claw.
 7. An image forming system comprising: an image forming apparatus that forms an image on a sheet; and a sheet processing apparatus that stacks and processes sheets fed from the image forming apparatus, wherein the sheet processing apparatus is the apparatus as claimed in claim
 1. 